On the pinoresinol type of structural units in lignin

Ogiyama, Koichi; Kondo, Tamio

doi:10.1016/s0040-4039(00)72803-6

Cited by 3 publications

(6 citation statements)

References 4 publications

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“…1 H NMR (CD 2 Cl 2 , 500 MHz), δ H : 3.85 (1H, dd, J = 12.1, 4.0 Hz, γ 1 ), 3.95 (1H, dd, J = 12.1, 6.6 Hz, γ 2 ), 5.34 (1H, m, β), 6.33 (1H, broad-dd, J = 10, 2 Hz, A3), 6.42 (1H, br-dd, J = 10, 2 Hz, A5), 6.45 (1H, d, J = 8.9 Hz, α), 6.90 (2H, br-dd, J = 7, 1 Hz, B3 and B5), 6.98 (1H, br-td, J = 7, 1 Hz, B1), 7.10 (1H, br-dd, J = 10, 3 Hz, A2), 7.27 (2H, br-t, J = 7 Hz, B2 and B6), 7.61 (1H, br-dd, J = 10, 3 Hz, A6). 13 C NMR (CD 2 Cl 2 , 125 MHz) δ C : 65.4 (γ), 76.8 (β), 116.5 (B3 and B5), 122.5 (B1), 129.5 (A3), 130.3 (B2 and B6), 130.9 (A5), 133.9 (A6), 134.0 (A1), 142.0 (A2), 146.1 (α), 158.0 (B4), 187.3 (A4).…”

Section: H Nmr Spectrum (See Figures S3−s7 In the Si)mentioning

confidence: 99%

“…1 H NMR (CDCl 3 , 500 MHz), δ H : 3.82 (1H, dd, J = 12.1, 4.0 Hz, γ 1 ), 3.87 (3H, s, B3-OMe), 3.91 (1H, dd, J = 12.1, 6.9 Hz, γ 2 ), 5.19 (1H, m, β), 6.38 (1H, broad-d, J = 10 Hz, A3), 6.40 (1H, br-d, J = 12 Hz, A5), 6.53 (1H, d, J = 8.6 Hz, α), 6.85−6.87 (2H, m, B5 and B6), 6.92 (1H, d, J = 8.0 Hz, B2), 7.03 (1H, m, B1), 7.10 (1H, br-dd, J = 10, 2 Hz, A2), 7.47 (1H, br-dd, J = 10, 2 Hz, A6). 13 Compound QM-GG (Mixture of syn-and anti-Isomers, 7:3). Stereochemical assignments (syn-or anti-isomer) were made by comparison with the reported data of the same compounds, 44 typically by using the chemical shift data of the A2, A6, and A3-OMe protons.…”

Section: H Nmr Spectrum (See Figures S3−s7 In the Si)mentioning

confidence: 99%

“…1 H NMR (CDCl 3 , 500 MHz), δ H : major isomer, 3.77 (3H, s, A3-OMe), 3.88 (1H, broad-dd, J = 12, 4 Hz, γ 1 ), 3.98 (1H, br-dd, J = 12, 7 Hz, γ 2 ), 5.31 (1H, m, β), 6.22 (1H, d, J = 8.6 Hz, α), 6.40 (1H, d, J = 9.5 Hz, A5), 6.59 (1H, s, A2), 6.88 (2H, br-d, J = 8 Hz, B3 and B5), 6.98 (1H, m, B1), 6.99 (1H, m, A6), 7.26 (2H, br-t, J = 8 Hz, B2 and B6); minor isomer, 3.73 (3H, s, A3-OMe), 3.85 (1H, br-dd, J = 12, 4 Hz, γ 1 ), 3.95 (1H, br-dd, J = 12, 7 Hz, γ 2 ), 5.35 (1H, m, β), 6.21 (1H, s, A2), 6.31 (1H, d, J = 8.6 Hz, α), 6.50 (1H, br-d, J = 10 Hz, A5), 6.88 (2H, br-d, J = 9 Hz, B3 and B5), 6.98 (1H, m, B1), 7.26 (2H, br-t, J = 9 Hz, B2 and B6), 7.54 (1H, brd, J = 10 Hz, A6). 13 Compound QM-GS (Mixture of syn-and anti-Isomers, Majorand Minor-Isomer Ratio of 7:3). 1 H NMR (CDCl 3 , 500 MHz), δ H : major isomer, 3.72 (3H, s, A3-OMe), 3.75 (2H, broad-d, J = 4 Hz, γ), 3.82 (6H, s, B3-OMe and B5-OMe), 5.07 (1H, m, β), 6.43 (1H, br-d, J = 10 Hz, A5), 6.56 (1H, d, J = 8.6 Hz, α), 6.58 (1H, br-d, J = 2 Hz, A2), 6.59 (1H, br-d, J = 8 Hz, B2 and B6), 7.04 (1H, br-t, J = 8 Hz, B1), 7.09 (1H, br-dd, J = 10, 2 Hz, A6); minor isomer, 3.77 (3H, s, A3-OMe), 3.75 (2H, br-d, J = 4 Hz, γ), 3.82 (6H, s, B3-OMe and B5-OMe), 5.09 (1H, m, β), 6.30 (1H, br-d, J = 2 Hz, A2), 6.43 (1H, br-d, J = 10 Hz, A5), 6.58 (1H, br-d, J = 8 Hz, B2 and B6), 6.65 (1H, d, J = 8.9 Hz, α), 7.03 (1H, br-t, J = 8 Hz, B1), 7.51 (1H, br-dd, J = 2, 10 Hz, A6).…”

Section: H Nmr Spectrum (See Figures S3−s7 In the Si)mentioning

confidence: 99%

“…1 H NMR (CDCl 3 , 500 MHz), δ H : major isomer, 3.72 (3H, s, A3-OMe), 3.75 (2H, broad-d, J = 4 Hz, γ), 3.82 (6H, s, B3-OMe and B5-OMe), 5.07 (1H, m, β), 6.43 (1H, br-d, J = 10 Hz, A5), 6.56 (1H, d, J = 8.6 Hz, α), 6.58 (1H, br-d, J = 2 Hz, A2), 6.59 (1H, br-d, J = 8 Hz, B2 and B6), 7.04 (1H, br-t, J = 8 Hz, B1), 7.09 (1H, br-dd, J = 10, 2 Hz, A6); minor isomer, 3.77 (3H, s, A3-OMe), 3.75 (2H, br-d, J = 4 Hz, γ), 3.82 (6H, s, B3-OMe and B5-OMe), 5.09 (1H, m, β), 6.30 (1H, br-d, J = 2 Hz, A2), 6.43 (1H, br-d, J = 10 Hz, A5), 6.58 (1H, br-d, J = 8 Hz, B2 and B6), 6.65 (1H, d, J = 8.9 Hz, α), 7.03 (1H, br-t, J = 8 Hz, B1), 7.51 (1H, br-dd, J = 2, 10 Hz, A6). 13 General Procedure for Water Addition to QMs. 15 A dioxane solution of QM (3 mL), prepared as described above (originating from 0.3 μmol of β-O-4 dimer), was transferred into a 14 mL screwcap vial.…”

Section: H Nmr Spectrum (See Figures S3−s7 In the Si)mentioning

confidence: 99%

“…15 A positive correlation was clearly found between the S/G ratio and the erythro/threo ratio for the lignins of different hardwood wood species 16,17 and for reaction-wood lignins. 10,30,31 An NMR INAQUDEATE experiment on 13 C-enriched aspen lignin 29,32 revealed that the erythro form of β-syringyl ether structures is the most predominant of the four structural types (erythro-and threoβ-syringyl ethers and erythro-and threo-β-guaiacyl ethers). These findings indicated that the S-unit influences the diastereoselective addition of water to QMs and induces the erythro-preferential formation of β-O-4 structures in hardwood lignins.…”

Section: ■ Introductionmentioning

confidence: 99%

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Lignin-Biosynthetic Study: Reactivity of Quinone Methides in the Diastereopreferential Formation of p-Hydroxyphenyl- and Guaiacyl-Type β-O-4 Structures

Zhu

Akiyama

Yokoyama

et al. 2019

J. Agric. Food Chem.

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p-Quinone methides are involved in lignin biosynthesis as transient intermediates, and the aromatization step has a great impact on the chemical structure of the resulting lignin. A series of quinone methides (QMs) were synthesized and allowed to react with water in pH 3–7 buffers at 25 °C to mimic the formation of p-hydroxyphenyl- and guaiacyl-type (H- and G-type, respectively) β-O-4 structures in gymnosperm-plant cell walls. Water addition occurred in 3-methoxy-substituted QMs (G-type QMs) with half-lives of 1.4–15 min. In contrast, nonsubstituted QMs (H-type QMs) were very labile; they were aromatized to β-O-4 products with half-lives of only 10–40 s. The rapid aromatization in H-type QMs may provide an advantage over G-type species for efficiently driving the lignin-polymerization cycle, which possibly contributes to the development of highly lignified compression wood. In the water-addition reaction, the threo isomers of the β-O-4 products were stereopreferentially formed more than the erythro isomers from both G- and H-type QMs (erythro/threo ratios of 24:76 and 50:50, respectively). The proportion of erythro isomers was higher at lower-pH conditions. This pH-dependent trend agrees with findings from a previous study on 3,5-dimethoxy-substituted (syringyl-type, S-type) QMs; thus, this pH-dependent trend is common in H-, G-, and S-type lignin-related QMs. Higher threo-selectivity was obtained by changing the β-etherified aromatic rings from G- to H-type. A similar but weaker effect was also observed by changing the QM moiety from G- to H-type.

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Section: H Nmr Spectrum (See Figures S3−s7 In the Si)mentioning

confidence: 99%

Section: H Nmr Spectrum (See Figures S3−s7 In the Si)mentioning

confidence: 99%